Two speed cam shaft



Feb. 3, 1959 L. L. KERBY TWO SPEED CAM SHAFT 2 Sheets-Sheet 2 Filed Dec.4, 1956 INVENTOR. ZAWEEA CE Z. K525) BY United States Patent TWO SPEEDCAM SHAFT Lawrence L. Kerby, Hermosa Beach, Calif. Application December4, 1956, Serial No. 626,231

6 Claims. (Cl. 123-911) This invention relates to internal combustionengines, and more particularly to an internal combustion engine of thetype having poppet valves and provided with a longitudinally adjustablecam shaft having cam elements thereon selectively engageable with thepoppet valves so as to change the valve action in accordance withdifferent loading conditions imposed on the engine.

A main object of the invention is to provide a novel and improvedadjustable cam shaft system for an internal combustion engine, thesystem involving relatively simple parts, being easy to install, andenabling an operator to readily adjust an engine for efficient operationat different speeds.

A further object of the invention is to provide an improved internalcombustion engine of the type having poppet valves mounted forreciprocation and formed and arranged to control the admission of fuelinto the engine cylinders and the exhaust of products of combustionthere from, the engine being provided with a longitudinally adjustablecam shaft having different sets of cam elements thereon selectivelyengageable with the poppet valves to vary the action of the valves, inaccordance with different engine speeds, the engine being provided withmanually controlled means for shifting the cam shaft longitudinally andbeing further provided with means for locking the poppet valves inelevated positions during the adjustment of the cam shaft.

A still further object of the invention is to provide an improvedinternal combustion engine having a longitudinally movable cam shaft,said cam shaft being provided with respective sets of cams selectivelyengageable with the poppet valves of the engine to establish proper.valve timing for different engine speeds, the engine being provided withmeans for manually adjusting the cam shaft and being further providedwith means acting simultaneously with the first-mentioned means fortemporarily locking the poppet valves in elevated positions to allow thecam shaft to be smoothly adjusted without interference from said poppetvalves.

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings, wherein:

Figure 1 is a fragmentary longitudinal vertical cross sectional viewtaken through a portion of an internal combustion engine including anumber of poppet valves and showing a portion of an improved multipleelement cam shaft according to the present invention.

Figure 2 is an enlarged cross sectional detail view taken fluid pressurecontrol system employed in the present invention for controlling theadjustment of the cam shaft and for providing a poppet valve lockingaction during said adjustment.

Figure 7 is an enlarged cross sectional view taken on the line 7-7 ofFigure 6.

Figure 8 is an enlarged transverse vertical cross sectional view takenthrough the manually operated reversing valve of the system of Figure 6on the line 8-8 of Figure 6.

Figure 9 is a fragmentary elevational view of a portion of the cam shaftshifting arm employed in the system of Figure 6 and showing theyieldable detent means employed therewith to hold the cam shaft shiftingarm yieldably in an adjusted position.

Figure 10 is a cross sectional view taken on the line 10-10 of Figure 9.

Referring to the drawings, 11 generally designates an internalcombustion engine of the type having a plurality of cylinders and havingrespective pairs ofpoppet valves 12, 13 mounted for reciprocation in theengine and formed and arranged to control the admission of fuel into theengine cylinders and to exhaust the products of combustion therefrom.

Designated at 14- is a cam shaft which is rotatably and slidably mountedin the engine below the poppet valves 12, 13, the cam shaft beingprovided with respective sets of earns 15, 16 adapted to engage the camlifters for the respective poppet valves 12, 13, shown at 17, 18, tocontrol the opening and closing of the fuel inlet valve 12 and theexhaust valve 13 in the proper timed sequence, the cams being suitablyangularly spaced around the axis of the cam shaft for the different setsof valves 12, 13 for the respective cylinders, in a manner well known inthe art.

As shown in Figures 1, 2 and 4, each valve is provided with a cam lifterelement 17 or 18, the lifter 18 being illustrated in Figure 2, eachlifter comprising a cylindrical block 19's1idably mounted forreciprocation in a bore 20 formed in the engine block and biaseddownwardly toward its associated cam by a coiled spring 21 surroundingthe shank of the associated valve and bearing between the top wall ofbore 20 and the cylindrical block 19. Each cam lifter block is heldagainst rotation by the provision of a vertical groove 22 formed in itsbore 20 in which is slidably engaged a pin 23 secured in the block andprojecting radially therefrom. Opposite the pin 23, the lifter block isformed with an arcuate groove 24 adapted to receive the end of a lockingpin 25 when the block is in an elevated position, as will be presentlydescribed, whereby the valve lifter may be held in a position wherein itwill not interfere with cam shaft 14 when the cam shaft is shifted.

The cam shaft 14 is formed adjacent the respective earns 15 and 16 withadditional cams 15 and 16 adapted to engage the cam lifters 17 and 18when the cam shaft is shifted longitudinally to provide a modified valveaction and thus to provide a different type of engine performance. Thus,when the earns 15 and 16 act on the lifters 17 and 18, the engine mayprovide performance suitable for low or moderate speeds, such as undercity traffic conditions. When the cams 15 and 16 are employed to act onthe lifters 17 and 18, the engine performance may be that required forhigh speed or heavy loading conditions, such as for climbing steep hillsor for operating the associated motor vehicle at high speeds.

Cam shaft 14 is driven from the engine crank shaft in any suitablemanner, for example, by the provision of a drive shaft 26 coupled to theengine crank shaft, said drive shaft being provided with a pinion gear27 meshing with a larger gear 28 rotatably supported in the engine inany suitable manner and splined to the cam shaft by the provision of asplined portion 30 on the cam shaft which slidably engages through acorrespondingly splined central aperture in the gear 28. The splined camshaft portion 30 also drives a worm gear 31 which is in turn coupled tothe distributor worm shaft 32, whereby the engine distributor 33 isdriven synchronously with the cam shaft 14.

Secured to the end of the splined portion 30, externally of the engineblock is an inner bearing ring 34, saidinner bearing ring being mountedon the reduced shaftend portion 35, as shown in Figure 1, beingsecuredthereon by a nut 35 threaded on said reduced end portion andclampingly engaging the ring.

The bearing ring 3 is rotatably mounted within an outer bearing ring 37,being journaled thereto by ball bearings 33 positioned in opposingannular raceways formed in the bearing rings 34 and 37, providing anantifriction connection between the ring 37 and the earn. shaft 14. Ayoke member 3f is pivoted to the outer ring 37, as by diametricallyopposite pivot pins. 46, 4-0 rotat ably connecting the arms of yokemember 3% to diametrically opposite portions of the outer bearing ring37, as shown in Figures 1 and 5. The yoke 39 is rigidly secured to theend of an arm 41 pivoted in any suitable manner to the vehicle frame forrotation around an axis spaced from and perpendicular to the axis of thecam shaft, whereby rotation of arm 41 shifts the cam shaftlongitudinally.

Connected to the arm 41, as by a collar member 42 is a shift arm 43,which may be actuated in any suitable manner, for example, by fluidpressure means, as will be presently described, for shifting the camshaft 14.

Mounted in the engine block 11 perpendicular to and adjacent each valvelifter is a horizontal sleeve member 44 in which the associated lockingpin is axially positioned. As shown in Figure 2, each locking pin 25 iscarried on a circular piston element 46 slidably engaged in theassociated sleeve 44, each pin having a shank portion 47 projecting intoan auxiliary cylinder member 48 provided in the sleeve 44, each shankelement 47 having a head portion 49 slidably engaged in the associatedauxiliary cylinder 48. Each cylinder 48 is rigidly secured to an annularring member 50 which surrounds the associated shank 47 and which isslidably supported in the associated sleeve 44.

A first coiled spring 51 surrounds the pin 25, bearing between thepiston element 46 and the opposing wall of the bore of the engine block,biasing the pin member away from its associated valve lifter, namely, ina direction to the left, as viewed in Figure 2. A second coiled spring52 surrounds the shank 47, bearing between the associatedrpiston 46 andthe annular ring member 50, serving to transmit the force of spring 51to the auxiliary cylinder48. The central aperture of ring 50 issubstantially smaller than the diameter of the head 49, whereby movementof the ring member 50 to the left, as viewed in Figure 2, will urge thehead 49 to the left, and will act to withdraw the pin 25 from thearcuate notch 24 of its associated valve lifter when there is noopposing force applied to the associated auxiliary cylinder 48.

Axial'ly secured to each auxiliary cylinder 48 is a rack bar 54 whichmeshingly engages with an associated pinion gear 56 secured on a shaft57 rotatably mounted, in any suitable manner, and supported on theengine 11.

As will be apparent from Figure 2, when the shaft 57 rotates clockwise,as viewed in Figure 2, the rack gear 54 is urged to the right, wherebythe auxiliary cylinder 48 exerts a force on the annular ring member 50,which is transmitted by spring 52 to piston member 46, whereby thelocking pin 25 is urged to the right, as viewed in Figure 2, and willenter the annular groove 24 in the associated valve lifter when saidvalve lifter is elevated, for example, to its uppermost position shownin Figure 2, and will be maintained in elevated position as long as theclockwise torque continues on shaft 57.

It will be understood that each of the valve lifters 17 and1-8.associated with the various poppet valves of the engine is providedwith means-such as is illustrated in Figure 2, including a locking pin25, adapted to lockingly engage with the associated valve lifter toretain the valve lifter in its elevated position, substantially clear ofthe cam shaft, when its associated rack bar 54 is moved inwardly by theclockwise rotation of shaft 57, said shaft 57 acting simultaneously onall the rack bars, so that the locking action is simultaneously providedon all the valve lifters.

It will be understood that the grooves 24am located so that the pins 25can only enter said grooves when the associated valve lifter blocks havebeen elevated to their highest positions by the respective cams on thecamshaft. Thus, when it is desired to shift the cam shaft, by rotatingthe pivoted arm 41 by means of its actuating bar 43, torque is appliedto the shaft 57, to simultaneously urge the respective locking pins 25inwardly toward their associated valve lifter blocks 19, and the valvelifter blocks will become locked in their elevatedv positionssequentially as they reach such positions responsive to the action oftheir associated cams. The valve lifter blocks will be subsequentlymaintained elevated, allowing the cam shaft to be freely shifted untilthe torque is removed from the shaft 57, whereby the springs 51 will actto retract the lockiug pins 25 from the grooves 24 and will release thevalve lifters for cooperation with the new set of earns.

Referring now to Figures 6 to 10, a typical installation is disclosed,for example, in a motor vehicle, the shaft 57 being shown as journaledin brackets 58, 58 and being provided with a pinion gear 59, which isengaged by a rack bar 68. The rack bar 60 is carried on a piston rod 61which extends from a piston 62 mounted in a fluid pressure cylinder 63.Cylinder 63 is suitably mounted on the vehicle frame and has connectedto its top end a conduit 64 leading from the discharge end of a maincylinder 65. Cylinder 65 is provided with a piston 66 slidably mountedin a chamber 67, the piston being provided with the piston rod 68 whichis connected by a link bar 69 to the depending arm 70 of a bell crank71. Bell crank ing through an aperture 74- in the vehicle floorboard andprovided at its top end with a pedal 75. Bell crank 71 may be biasedcounterclockwise, as viewed in Figure 6, in any suitable manner, forexample, by the provision of a biasing spring 76 connecting arm 72 tothe vehicle floorboard, as shown, whereby the piston 66 is biased-to theright, as viewed in Figure 6, and will be movedto the right when thepedal 75 is released.

The main cylinder 65 is provided with the upper reservoir portion 77,and communicates with the chamber 67 by the provision of an aperture 78adjacent the right end of main cylinder 65, as viewed in Figure 6.

Designated at 79 is a control valve, comprising a cylindrical body 80 inwhich is rotatably mounted a sectorshaped rotor 81, said rotor beingprovided with the external actuating shaft 82 centrally secured to theoperating disc 83. The operating disc 83 may be rotated in any suitablemanner, for example, by a link bar 84 connected to a suitable manualcontrol element, for example, a lever located adjacent the operator ofthe vehicle.

The valve 79 is of the duplex two-way type, comprising a first set ofports 85 and 86 located adjacent one end of cylinder 80 and angularlyspaced by an amount slightly less than the angle subtended by the sectormember 81, whereby port 85 may be selectively placed in communicationeither with port 86 or with a bottom port 88 provided in the cylindricalbody 80.

An additional pair of ports 39 and are provided in body 80,longitudinally aligned with the respective ports 1 85 and'86, andlocated adjacent the opposite end of the body 80, the port 89 beingadapted to be selectively placed in .communication with port 90 or witha bottom port 91 provided in the cylindrical valve body 80 inlongitudinal alignment with the bottom port 88.

The cam shaft shift arm 43 is connected to a piston 93 slidably mountedin a fluid pressure cylinder 94 suitably mounted on the vehicle frame.The right end of cylinder 94, as viewed in Figure 6, is connected by aconduit 95 to port 90 of valve 79 and is further connected by a conduit96 to the bottom port 88 at the left end of the cylindrical body 80 ofthe valve 79. The left end of the cylinder 94 is connected to port-86 bya conduit 97 and is further connected to bottom port 91 by a conduit 98.

Normally, the valve control disc 83 is in a neutral position, as shownin Figure 8, wherein the respective ports 85, 86, and 89, 96 arecovered. Assuming that it is desired to shift the cam shaft 14 to theright, as viewed in Figure 1, namely, in a direction to substitute thecams 16' and 15' for the cams 16 and 15, the locking control arm 84 ismoved in a direction to place ports 89 and 85 in communication withbottom ports 91 and 88, namely, to rotate the valve rotor 81 clockwise,as viewed in Figure 8. Foot pressure is then applied to the pedal 75,causing the piston 66 to force fluid through conduit 64 into the top endof cylinder 63, moving the piston 62 downwardly. Downward motion ofpiston 62 causes rack bar 60 to rotate pinion 59 and to thus rotate thevalve lifter locking shaft 57 in a direction to rotate the associatedpinions 56 clockwise, as viewed in Figure 2 and to move the rack bar 54associated therewith inwardly toward their associated valve lifters 19.The valve lifters become locked in elevated positions, by the pins 25 inthe manner above described, and ultimately, with continued foot pressureapplied to pedal 75, the piston 62 moves to the lower portion ofcylinder 63 allowing the fluid to escape therefrom through a conduit 99connecting the portion of cylinder 63 just above the lowermost positionof piston 62 to the valve port 89. The fluid .under pressure then passesthrough conduit 98 into cylinder 94 and acts on piston 93 to move theshift arm 43 to the right, as viewed in Figure 6, and also to move camshaft 14 to the right as viewed in Figure 1, causing the cam shaft to beshifted longitudinally to bring cams 16 and 15 beneath the valve lifters18 and 17. Fluid discharges from the right end of cylinder 94 throughconduit 96 into the body of valve 79 and thence through port 85 and aconduit 100 connected thereto to the reservoir 77 of the main cylinder65. When the foot pressure applied to the pedal 75 is released, coiledspring 76 acts to elevate the pedal and also acts to return piston 66 tothe right end of chamber 67. The springs 51 act to re tract the lockingpins 25 from the grooves 24 and to extend the rack bars 54, causing thepinion 56 to rotate the shaft 57 counterclockwise, a viewed in Figure 2.This elevates the rack bar 60 and causes the piston 62 to return to itsnormal, elevated position in cylinder 63. Shift arm 43 tends to remainin its adjusted position, since conduit 99 is closed off by theelevation of the piston 62 and there is no further force acting on thepiston 93.

The bottom of cylinder 63 is connected to the fluid return line 100 by aconduit 120 to allow fluid to return to reservoir 77 when piston 62descends.

Preferably, releasable retaining means is provided for retaining theshift arm 43 in adjusted position. Thus, the shift arm 43 may haverigidly secured thereto a block member 101, at an intermediate portionof the shift arm 43, the block member 101 extending slidably through abracket member 102 secured to the vehicle frame, said bracket memberincluding an arm 183 transversely overlying the block member 101. Thearm 103 is formed with a recess in its intermediate portion, shown at104, in which is mounted a coiled spring 105 acting on a ball detent 106of conventional structure, the ball detent being selectively engageablein a pair of spaced recesses 107 and 108 formed in the block 101, andcorresponding to the two diiferent positions of adjustment of the shiftarm 43, namely, a first position wherein the cams 15 and 16 are locatedbeneath the valve lifts 17 and 18, and a sec- 6. 0nd position whereinthe cams 15' and 16 are located beneath the valve lifters 17 and 18.

The block member 101 is supported for sliding movement with respect tothe bracket member-102 in any suitable manner, for example, byrespective sets of link bars 110, 111 loosely connected to the oppositeend portions of the block member 101, as by pins 112, and pivotedrespectively to the top and bottom corner portions of the bracket member102 by pivot pins shown respectively at 113 and 114.

After the shift arm 43 has been moved to its selected position, in themanner above described, the valve 79 is returned to its neutral positionby rotating the control disc 83 to move the sector-shaped valve body 81to its neutral position, shown in Figure 8.

When it is desired to reverse the operation above described, namely, toreturn the shift arm 43 to its initial position, wherein cams 15 and 16are positioned below lifter members 17 and 18, the same procedure abovedescribed is employed except that the disc 83 is rotated in a directionto block ofi the bottom ports 91 and 88 and to connect port 89 to port90 and port to port 86. Thus, when piston 62'descends, the fluid underpressure from cylinder 63 passes through conduit 99 and through ports 89and 98 to conduit 95, entering the right end of cylinder 94 and exertingforce on piston 93 to move shift arm 43 to the left. Fluid from theforward end of cylinder 94 discharges through conduit 97 and throughports 86 and 85 to the return conduit 100, being thus returned to thereservoir 77. Previous to this, the same valve lifter locking actionpreviously described occurs, since shaft 57 is rotated by the downwardmovement of the piston 62 caused by depression of the pedal 75.

It will be understood that the duplex two-way valve 79 comprises twoseparate chambers 113' and '114', the chamber 113 containing the ports85, 86 and 88 and the chamber 114' containing the ports 89, and 91.

While a specific embodiment of an improved cam shaft shifting means foran internal combustion engine has been disclosed in the foregoingdescription, it will be understood that various modifications within thespirit of the invention may occur to those skilled in the art.Therefore, it is intended that no limitations be placed on the inventionexcept as defined by the scope of th appended claims: a

What is claimed is:

1. In an internal combustion engine, poppet valves mounted forreciprocation and formed and arranged to control the admission of fuelinto the engine cylinders and the exhaust of products of combustiontherefrom, a cam shaft rotatably and slidably mounted in the enginebeneath the valves and having at least two cams selectively movablebeneath each poppet valve responsive to longitudinal movement of the camshaft, spring means biasing the poppet valves into engagement with saidcam shaft, respective locking pins slidably mounted in the engineadjacent to and perpendicular to the valves, said valves being formedwith respective recesses located to receive said pins when the valvesare elevated substantially to their uppermost positions, means foradjusting said cam shaft longitudinally, means urging said pins awayfrom said valves, and manually operated means formed and arranged tosimultaneously move said pins toward engagement with said valves forentry into said recesses and to releasably lock the poppet valves inelevated positions during the longitudinal adjustment of the cam shaft.

2. In an internal combustion engine, poppet valves mounted forreciprocation and formed and arranged to control the admission of fuelinto the engine cylinders and the exhaust of products of combustiontherefrom, a-

cam shaft rotatably and slidably mounted in the engine beneath thevalves and having at least two cams selectively movable beneath eachpoppet valve responsive to longitudinal movement of the cam shaft,spring means biasing the poppet valves into engagement with said camshaft, respective locking pins slidably mounted in the engine adjacentto and perpendicular to the valves, said valves being formed withrespective recesses located to receive said pins when the valves areelevated substantially to their uppermost positions, spring meansbiasing said pins away from said recesses, means for adjusting said camshaft longitudinally and manually operated means formed and arranged tosimultaneously move said pins toward engagement with said valves forentry into said recesses against the force of said last-named springmeans to releasably lock the poppet valves in elevated positions duringthe longitudinal adjustment of the cam shaft.

3. In an internal combustion engine, poppet valves mounted forreciprocation and formed and arranged to control the admission of fuelinto the engine cylinders and the exhaust of products of combustiontherefrom, a cam shaft rotatably and slidably mounted in the enginebeneath the valves and having at least two cams selectively movablebeneath each poppet valve responsive to longitudinal movement of the camshaft, spring means biasing the poppet valves into engagement with saidcam shaft, respecive locking pins slidably mounted in the engineadjacent to and perpendicular to the valves, said valves being formedwith respective recesses located to receive said pins when the valvesare elevated substantially to their uppermost positions, spring meansbiasing said pins away from said recesses, means for adjusting said camshaft longitudinally, spring means biasing said pins away from saidrecesses, respective rack bars axially connected to said pins, a shaftrotatably mounted adjacent said rack bars, pinion gear means on saidlast-named shaft meshing with said rack bars, and means formed andarranged to rotate said last-named shaft in a direction tosimultaneously move said pins toward engagement with said valves forentry into said recesses against the force of said last-named springmeans to releasably lock the poppet valves in elevated positions duringthe longitudinal adjustment of the cam shaft.

4. In an internal combustion engine, poppet valves mounted forreciprocation and formed and arranged to control the admission of fuelinto the engine cylinders and the exhaust of products of combustiontherefrom, a cam shaft rotatably and slidably mounted in the enginebeneath the valve and having at least two cams selectively movablebeneath each poppet valve responsive to longitudinal movement of the camshaft, spring means biasing the poppet valves into engagement with saidcam shaft, respective locking pins slidably mounted in the engineperpendicular to the valves, said valves being formed with respectiverecesses located to receive said pins when the valves are elevatedsubstantially to their uppermost positions, fluid pressureoperated meansformed and arranged to adjust said cam shaft longitudinally, springmeans biasing said pins away from said recesses, respective rack barsaxially connected to said pins, a shaft rotatably mounted adjacent saidrack bars, pinion gear means on said last-named shaft meshing with saidrack bars, and means controlled by said fluid pressure-operated meansand formed and arranged to rotate said lastnamed shaft in a direction tosimultaneously move said pins toward engagement with said valves forentry into said recesses against the force of said last-named springmeans to releasably lock the poppet valves in elevated positions duringthe longitudinal adjustment of the cam shaft.

5. In an internal combustion engine, a plurality of poppet valvesmounted for reciprocation and formed and arranged to control theadmission of fuel into the engine cylinders and the exhaust of productsof combustion therefrom, a cam shaft rotatably and slidably mounted inthe engine and having at least two cams selectively movable beneath eachpoppet valve responsive to longitudinal movement of the cam shaft, meansbiasing the poppet valves into engagement with the cam shaft, respectivelocking pins slidably mounted in the engine perpendicular to the valves,said valves being formed with locking recesses located to receive saidpins when the valves are elevated substantially to their uppermostpositions, spring means biasing said pins away from the recesses,respective rack bars axially connected to the pins, a shaft rotatablymounted adjacent said rack bars, pinion gear means on said last-namedshaft meshing with said rack bars, a rotary control arm coupled to saidcam shaft, fluid pressure means operatively connected to said controlarm formed and arranged to rotate said control arm and to shift said camshaft longitudinally, and further fluid pressure-operated means formedand arranged to rotate said last-named shaft against the force of saidspring means simultaneously with the operation of said firstnamed fluidpressure means, whereby to move said pins simultaneously toward saidvalves for entry into said recesses to releasably lock said poppetvalves in elevated positions during the longitudinal adjustment of thecam shaft.

6. In an internal combustion engine, a plurality of poppet valvesmounted for reciprocation and formed and arranged to control theadmission of fuel into the engine cylinders and the exhaust of productsof combustion therefrom, a cam shaft rotatably and slidably mounted inthe engine and having at least two cams selectively movable beneath eachpoppet valve responsive to the longitudinal movement of the cam shaft,means biasing the poppet valves into engagement with the cam shaft,respective locking pins slidably mounted in the engine perpendicular tothe valves, said valves being formed with locking recesses located toreceive said pins when the valves are elevated substantially to theiruppermost positions, spring means biasing said pins away from therecesses, respective rack bars axially connected to the pins, a shaftrotatably mounted adjacent said rack bars, pinion gear means on saidlast-named shaft meshing with said rack bars, a rotary control armcoupled to said cam shaft, fluid pressure means operatively connected tosaid control arm formed and arranged to rotate said control arm and toshift said cam shaft longitudinally, further fluid pressure-operatedmeans formed and arranged to rotate said last-named shaft against theforce of said spring means simultaneously with the operation of saidfirst-named fluid pressure means, whereby to move said pinssimultaneously toward said valves for entry into said recesses toreleasably lock said poppet valves in elevated positions during thelongitudinal adjustment of the cam shaft, and yieldable detent meansengaging said control arm and yieldably holding said control arm inadjusted position.

References Cited in the file of this patent FOREIGN PATENTS 736,098France Nov. 18, 1932 536,746 Great Britain May 26, 1941 748,505 GermanyNov. 3, 1944 l g v a

